feat(tvix/eval): Box Value::Catchable

This is now the only enum variant for Value that is larger than 8
bytes (it's 16 bytes), so boxing it (especially since it's not
perf-critical) allows us to get the Value size down to only 16 bytes!

Change-Id: I98598e2b762944448bef982e8ff7da6d6683c4aa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10798
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: aspen <root@gws.fyi>

tvix/eval/src/compiler/mod.rs

@@ -399,9 +399,9 @@ impl Compiler<'_> {
             // TODO: decide what to do with findFile
             if raw_path.len() == 2 {
                 return self.emit_constant(
-                    Value::Catchable(CatchableErrorKind::NixPathResolution(
+                    Value::Catchable(Box::new(CatchableErrorKind::NixPathResolution(
                         "Empty <> path not allowed".into(),
-                    )),
+                    ))),
                     node,
                 );
             }